1. Field of the Invention
The present invention relates to a hollow golf club head.
2. Description of the Related Art
Wood and utility (hybrid) type golf club heads with hollow constructions have been proposed. Japanese Patent Laid-Open Nos. 9-154985 and 2001-187174 disclose golf club heads of those types, which are reinforced with ribs. Also, Japanese Patent Laid-Open No. 2005-137788 discloses a golf club head with its total distance performance improved by setting the thicknesses of the crown and sole portions locally small. Japanese Patent Laid-Open No. 2005-6698 discloses a golf club head having a face portion with its repulsion performance improved by setting the rigidity of its middle portion in the toe-to-heel direction relatively low on the front edge in the crown portion. Japanese Patent Laid-Open No. 2008-154624 discloses a golf club head having a face plate which partially extends to the crown and sole portions to reduce a decrease in total distance upon an off-center hit.
Great importance is often attached to the total distance performances of wood and utility type golf club heads, so these heads must obtain more stable total distances. The total distance of a struck golf ball is related to the striking point on the face portion of this ball. An average golfer is likely to strike golf balls at varying striking points, and, in turn, is likely to obtain varying total distances. Nevertheless, the variation in striking point has a certain tendency.
The golf club head described in Japanese Patent Laid-Open No. 2008-154624 has a face plate which extends to the crown portion on its toe side and to the sole portion on its heel side to reduce a decrease in total distance upon an off-center hit by means of flexure of the face plate.
However, an athletic golf club head often has a face plate that flexes a small amount to comply with the regulation of the repulsion force of the face portion (SLE rule). In this arrangement, the golf club head described in Japanese Patent Laid-Open No. 2008-154624 may not be able to sufficiently reduce a decrease in total distance upon an off-center hit.